components rendered on top of actionbar in blank application

Steps to reproduce:
1.create a blank application in mobile project.
2.add
<s:ActionBar width="100%"/>

<s:HGroup >
<s:Button label="button" />
<!-<s:HSlider id="myHSlider"/>->
</s:HGroup>
3.compile and run.

Actual Results:
the button rendered overlapping the actionBar.

Expected Results:

Workaround (if any):